Hard metal alloy



Patented Feb. 9, 1937 PATENT OFFICE HARD METAL ALLOY Alan Richard Powell and Ernest RobcrtBox,

London,

England, assignors to Johnson Matthey & Company Limited, London, England, a. British company No Drawing. Application October 4, 1933, Serial No. 692,219. In Great Britain October 11,

v 9 Claims.

This invention relates to the manufacture and production of hard metal alloys especially useful for tipping the points of gold nibs and the points of compass needles. Such alloys in addition to great hardness must be resistant to tarnishing and to corrosion by dilute solutions of the common acids and alkali, must have a high resistance to wear, must be capable of being readily soldered onto gold and onto copper and iron base metal alloys and must be sufiiciently tough not to chip or splinter when subjected to grinding, polishing or slitting operations. At one time native grains of osmiridium were solely used for these purposes but the supplies of this natural product are not sufiiciently uniform in size and shape; hence numerous alloys have been made for this purpose by melting together some or all of the constituents of osmiridium with other metals of the platinum group with or ,without the addition of base metals to increase the hardness. Efiorts to convert native osmiridium into grains suitable for tipping nibs by melting the alloy alone or with the addition of other constituents have so far not produced grains of a quality equal to that of native grains.

We have now found that suitable alloys for the said purposes may be made by melting native or synthetic osmiridium (by which is meant throughout the specification and claims an alloy of 40 to 60 per cent of osmium) 60 to 40 per cent of iridium and to 20 per cent of ruthenium or of osmium and/or ruthenium together with at least one hardening agent selected from each of the three following groups; (a) the group consisting of cobalt and'nickel (3 to 25 per cent) (b) tungsten (an appreciable but efi'ective amount up to 40 per cent) and (c) boron (0.1 to per cent). The alloy should contain at least 40 per cent of osmiridium or of osmium and/or ruthenium. The remaining constituents depend on the proportion of osmiridium or osmium and/or ruthenium in the alloy. Substitution of part of the element of group (a) by a corresponding amount of an element of group (b) hardens the alloy only to a small extent but increases the hardness considerably when more than about 0.5 per cent of an element of group (0) is present.

When the alloy contains less than about '75 per cent of osmiridium we prefer to use a combination of elements of groups (a) and (b) as the greater part of the remainder, together with a small quantity as for example less than 2 per cent of an element of group (0) as a deoxidizing agent, or up to 5 per cent as a combined deoxidizing and hardening agent. The relative proportions of elements of group (a) and (b) used in the alloys inthis case vary between 1:5 and 5:1 and we have obtained the best results by the use of cobalt and tungsten in the ratio of 3:1 or 1:3 together with boron as additional hardening agent; this forms tungsten boride which is an intensely hard compound and imparts high wear resisting properties to the alloys.

osmiridium or' an equivalent amount of. osmium and/or ru- Percent thenium 45 to94.5 Tungsten 0 to 40 Cobalt and/or nickel 5 to25 Boron 0.5 to 3 The following example gives the percentage compositions of alloys which have proved very satisfactory but the invention is not restricted to this example.

Example Per cent Native osmiridium 50 Cobalt 12 Tungsten 36 Boron, the boron being added in the form of cobalt boride 2 What we claim is:-

1. A hard metal alloy of the kind defined consisting of 40 to 94.5% of at least one metal of the group consisting of osmiridium, osmium, and ruthenium together with at least one hardening agent of each of the following groups: 3 to 25% of (a) cobalt and nickel, an appreciable but efiective amount up to 40% of (b) tungsten and 0.5 to 5% of (c) boron.

2. A hard metal alloy of the kind defined consisting of 40 to 94.5% of osmiridium, 3 to 25% of a metal of the group consisting of cobalt and nickel, an appreciable but effective amount up to 40% of tungsten, and 0.5 to 5% of boron..

3. A hard metal alloy of the kind defined consisting of 40 to 94.5% of osmium, 3 to 25% of a metal of the group consisting of cobalt and nickel,

an appreciable but eflective amount up to 40% of tungsten, and 0.5 to 5% of boron.

4. A hard metal alloy of the kind defined conaisting of 40 to 94.5% of ruthenium; to 25% of a metal or the group consisting of cobalt and nickel, an appreciable but efiective amount up to 40% of tungsten, and 0.5 to 5% of boron.

5. A hard metal alloy of the kind defined consisting of 40 to 94.5% of at least one metal of the group consisting of osmiridium, osmium and ruthenium, 3 to 25% of cobalt, an appreciable but efiective amount up to 40% of tungsten and 0.5

to 5% of boron. 6. A hard metal alloy of the kind defined consisting of 40 to 94.5% of at least one metal of the a group consisting of osmiridlum, osmium and ruthenlum, 3 to 25% of nickel, an appreciable but eflective amount up to.40% oi tungsten and 0.5 to 5% of boron.

7. A hard metal alloy of the kind defined consisting of 40 to 50% of at least one metal of the 

